T1 Independent, T2* Corrected MRI With Accurate Spectral Modeling for Quantification of Fat: Validation in a Fat-Water-SPIO Phantom

Purpose: To validate T-1-independent, T-2*-corrected fat quantification technique that uses accurate spectral modeling of fat using a homogeneous fat-water SPIO phantom over physiologically expected ranges of fat percentage and T-2* decay in the presence of iron overload. Materials and Methods: A homogenous gel phantom consisting of vials with known fat-fractions and iron concentrations is described. Fat-fraction imaging was performed using a multiecho chemical shift-based fat-water separation method (IDEAL) and various reconstructions were performed to determine the impact of T-2* correction and accurate spectral modeling. Conventional two-point Dixon (in-phase/out-of-phase) imaging and MR spectroscopy were performed for comparison with known fat-fractions. Results: The best agreement with known fat-fractions over the full range of iron concentrations was found when T-2* correction and accurate spectral modeling were used. Conventional two-point Dixon imaging grossly underestimated fat-fraction for all T-2* values, but particularly at higher iron concentration. Conclusion: This work demonstrates the necessity of T-2* correction and accurate spectral modeling of fat to accurately quantify fat using MRI.